This invention relates to an extrusion die for making flat products having an equally smooth surface on either side and regular edges.
The manufacture of products in strip form by the cooking/extrusion/expansion process is known. CH-PS No. 624 604 relates to an extrusion die comprising upstream of the extrusion nozzle a grid arranged in an intermediate position in the front chamber between the tip of the screw of the extruder and the pressure equalization chamber. This die can only be used with an extruder comprising two co-rotating screws. On the other hand, since the screw bears directly against the counter-pressure grid, the wear of the head of the screw of the extruder leads to an irregular product on account of the play which exists between the screw head and the counter-pressure grid. With regard to the product obtained, it is not equally smooth on either side and has a tendency towards arching and towards deformation on account of inner tensions.